1. Field of the Invention
This invention relates in general to a plurality of regeneration circuits comprising at least two clock regeneration circuits wherein the regeneration circuits are respectively provided for mutually different clock frequencies and each regeneration circuit contains at least one SAW (surface acoustic wave) filter module to which a clock extraction circuit applies at the input pulses acquired from the data pulses.
2. Description of the Prior Art
Clock regeneration circuits have been realized for some time using band pass filters which are fed with pulses that are derived from the received data pulses. For example, U.S. Pat. No. 4,004,162 discloses a clock regeneration circuit wherein the data pulses received from the regeneration circuit are edited and then supplied to a band-pass filter using a clock extraction circuit which principally comprises a differentiating circuit and a rectifier arrangement following the differentiating element. The band-pass filter has a center frequency which is tuned to the clock frequency of the data pulses. The output pulses of the clock extraction circuit excite the band-pass filter at oscillations which have the frequency of the signal clock. A clock signal can be acquired from such oscillations and the incoming data pulses which have their pulse shape obliterated are capable of being regenerated in proper phase using the clock signal.
The band-pass filter in such a clock regeneration circuit has often been recently realized by a filter which works with acoustic surface waves and see, for example, the article IEEE, Journal on Selected Areas in Communications, Vol. SAC- 2, No. 6, November 1984, Pages 957-965.
Also, the increasing employment of pulse coded data transmission particularly in what is referred to as light waveguide transmission technology requires that a relatively large number of clock regeneration circuits are required in such systems.
See also French patent No. 1,603,165, U.S. Pat. No. 4,027,178, Article entitled "Optical Fiber Repeated Transmission Systems Utilizing SAW Filters" IEEE Transactions on Sonics and Ultrasonics, Vol. 30, No. 3, May 1983, Pages 119-126 and Journal of Light Wave Technology, Vol. LT-2, No. 6, Dec. 1984, Pages 895 to 900.